This invention pertains to a ball having rotation produced by an internal mechanism. It is well known that a sphere in flight will have a curved path of travel if the sphere is rotating. The amount of spin that a novice can impart to a ball is limited. The present invention employs a mechanism within the ball to impart a rotational force to the thrown ball, independent of the rotational force which the thrower may place on the ball. Thus, a novice can throw a "curve ball" with relative ease.
An example of a ball having an increased rate of spin is U.S. Pat. No. 3,874,663 issued to Kahle. The toy ball of Kahle discloses a hollow ball containing a diametrically extending tube. Two weights are slidably mounted within the tube. Springs urge the weights toward the center of the ball, while user controlled cords attached to the weights keep them apart when the user holds the ball. When the ball is thrown and the cords are released, the springs force the weights toward the center of the ball, thus concentrating the mass distribution of the ball near the center. The spin velocity of the ball increases in order to conserve angular momentum, and the curve of the ball is enhanced. Unlike the present invention, which produces a specific, distinct rotational force regardless of the rotational force, if any, applied to the ball by the thrower, the Kahle device merely enhances the natural rotational force imparted to the ball by the thrower.